The present invention relates to implantable medical leads, and more particularly, to leads designed for improved lead positioning and placement.
In medical diagnosis and treatment of various brain disorders, including epilepsy, Parkinson""s disease, sleep disorders, and psychiatric ailments, it is customary and frequently useful to analyze electrical signals originating in the brain. It is also becoming accepted to apply electrical stimulation to various structures of the brain for both diagnostic and therapeutic purposes. Furthermore, chronic electrical stimulation is contemplated as a direct treatment for various disorders. For example, an implantable neurostimulator that is coupled to an implantable medical lead having one or more deep brain electrodes or depth electrodes is described in U.S. Pat. No. 6,016,449 to Fischell, et al.
Generally, external equipment, such as a cranially implantable neurostimulator device, is connected to acutely implanted brain electrodes located on an implantable medical lead. Typical implantable medical leads are flexible small-diameter (usually 1-1.5 mm) round leads having one or more distal electrodes located coaxially along the distal end of the lead. It is also possible to employ an implantable medical lead having scalp electrodes instead of depth electrodes for certain types of electroencephalogram monitoring and analysis along the scalp; however, precise localization of the electrode is less feasible with scalp electrodes.
Generally, implantation of an implantable medical lead involves surgically exposing an insertion site in the cranium that is an operative distance from an electrode site. An electrode site may be chosen at any appropriate stage of the surgical procedure, including pre-surgically in an operative planning stage; intraoperatively after a craniotomy has been performed or a burr hole has been made; or intraoperatively after one or more other procedures, such as functional mapping, have been performed. After an insertion site is created, the lead is then inserted to the desired electrode site along a predetermined direction to a predetermined depth.
Common requirements for implantable medical leads include flexibility, strength, and durability. The extent of such qualities, of course, is dependent upon the nature of the use, for example, temporary or permanent implantation. While material selection and certain construction techniques can be tailored to assist in meeting these prescribed characteristics, one consideration in the design of implantable leads is increasing the ease with which the delicate lead is implanted.
A conventional lead placement technique is illustrated in FIGS. 1a-1d. Referring first to FIG. 1a, a traditional deep brain lead 10 is shown positioned in a desired deep brain structure 12 with the assistance of a cannula 14, a rigid tunneling and positioning tool capable of sliding over the brain lead 10. Positioning the lead 10 is complicated by the fact that existing leads do not provide a visual indicator showing how deep the lead 10 has been inserted and/or whether the lead 10 has been accidentally moved. Even one millimeter of travel of a properly positioned lead may cause unsatisfactory results. Accordingly, reliable methods and apparatus for locating the lead in the brain are necessary.
Referring now to FIG. 1b, after the cannula 14 and lead 10 is appropriately placed, the cannula 14 is retracted. While the cannula 14 is retracted, a stylet 16 inserted at a proximal end 18 of the lead 10 may be employed to hold the lead 10 in place. The lead 10 and its position within the brain must be continually monitored to ensure proper placement.
After the cannula 14 is retracted such that its distal end 20 is exposed as shown in FIGS. 1b and 1c, the physician grasps the exposed portion of the lead 10 adjacent to the distal end 20 of the cannula 14, holds it in position, and releases the stylet 16 so that the cannula 14 can be removed by sliding it longitudinally over the lead 10. If a split cannula is employed, it may be removed in a lateral direction without sliding the cannula longitudinally over the lead 10. However, removal of a split cannula in a lateral direction may risk damage to the delicate lead 10 as well as risk dislocation of the lead 10.
Finally, the stylet 16 must be removed without grossly affecting the position of the lead 10. A positioned lead 10 with the stylet 16 removed is shown in FIG. 1d. As can be seen in FIGS. 1a-1d, the length 22 of the lead 10 remaining outside the insertion site is approximately at least as long as the cannula 14 itself so that the lead 10 may be held in position during installation. However, the length 22 of the lead 10 that remains outside the brain may be too long for aesthetic reasons as well as for functional attachment to a cranially implanted neurostimulator device. Also, a long lead segment 22 outside the cranium may create a site for traction on the lead 10 potentially resulting in its dislocation and/or a site for potential damage to the lead 10 itself. In some circumstances, leads with an excess of coiled-up length may have an increased susceptibility to reliability problems.
In general, implanting a lead within the brain is difficult and, therefore, a lead that is easy to implant is desirable. A lead that is easier to implant improves the accurate localization of the electrode at a specific point of the brain. As a result, subsequent treatment can be carried out more precisely. Also desirable is a lead that advantageously has a minimal length of excess lead protruding from the insertion site.
In accordance with one aspect of the present invention, there is provided an implantable lead including a body having a proximal end and a distal end. At least one electrode is located at the distal end and connected to at least one terminal that is located at the proximal end. The lead includes a plurality of markings on the body.
In accordance with another aspect of the present invention, there is provided a method of implanting a lead. The method includes providing a lead that has a proximal end and a distal end. The lead has at least one electrode at the distal end that is connected to at least one terminal at the proximal end. The lead includes a plurality of markings located between the distal end and the proximal end. The method includes the step of determining an electrode site for stimulation. An insertion site is provided in the patient""s cranium and the lead is inserted into the insertion site. The lead is positioned and a visual indication of lead position is provided by the markings on the lead.
In accordance with yet another aspect of the present invention, there is provided an implantable lead comprising a lead portion having a proximal end and a distal end. The lead portion further includes a body between the proximal end and the distal end. The lead portion also includes at least one electrode at the distal end and at least one terminal at the proximal end. The at least one electrode is connected to the at least one terminal. The implantable lead further includes an extension removably connected to the lead portion. The extension has a proximal end and a distal end. The extension includes a body between the proximal end and the distal end.
In accordance with another aspect of the present invention, there is provided an implantable lead comprising a lead portion having a proximal end and a distal end. The lead portion further includes at least one electrode at the distal end electrically connected to at least one terminal at the proximal end. The implantable lead further includes an extension removably connected to the lead portion at a breakaway zone. The extension has a proximal end and a distal end.
In accordance with another aspect of the invention there is provided an implantable lead. The implantable lead includes a lead portion having a proximal end and a distal end. The lead portion includes at least one electrode at the distal end and at least one terminal at the proximal end. The at least one electrode is electrically connected to the at least one terminal. The implantable lead further includes an extension removably coupled to the lead portion. The extension has a proximal end and a distal end. The extension includes a sleeve portion that has a fixed end and a lead portion receiving end. The fixed end is fixed to the distal end of the extension. The lead portion is removably coupled within the lead portion receiving end of the sleeve.
In accordance with yet another aspect of the present invention, there is provided a method of implanting a lead in a patient""s brain comprising the step of providing a lead that has a lead portion and an extension. The lead portion is removably coupled to the extension. The lead portion has at least one electrode at a distal end that is electrically coupled to at least one terminal at the proximal end. The method further includes determining an electrode site for stimulation. An insertion site is provided in the patient""s cranium and a cannula is inserted into the patient""s brain. The lead is inserted into the cannula such that the distal end of the lead portion is inserted first. The lead is positioned at the electrode site and the cannula removed. The extension is removed from the lead portion.